ixgbe: create function to restart autoneg

This patch is for restarting auto negotiation on PHY.

Signed-off-by: Jakub Chylkowski <jakubx.chylkowski@intel.com>
Signed-off-by: Guinan Sun <guinanx.sun@intel.com>
Reviewed-by: Wei Zhao <wei.zhao1@intel.com>

Approved by: imp
Obtained from: DPDK (664ea2614eafbec8eda5c86764ff047475a1e5c6)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D31621

(cherry picked from commit 80a39a2bda8208c716f614f792c8d9a3628d6c26)